1. Field of the Invention
The present invention relates to a multi-functional cyclic silicate compound, a siloxane-based polymer prepared from the silicate compound and a process of producing an insulating film using the siloxane-based polymer. More specifically, the present invention relates to a multi-functional cyclic silicate compound capable of being converted into a polymer of low hygroscopicity and excellent mechanical properties, a siloxane-based polymer prepared from the silicate compound and a process of producing an insulating film using the siloxane-based polymer.
2. Description of the Related Art
As the degree of integration in semiconductor devices increase, the R(resistance)×C(capacitance) delay also increases, resulting in serious problems such as signaling transfer delays. Thus, how to reduce the capacitance of an interlayer insulating film has been a matter of great concern in the field of semiconductor production technology, and various attempts have been made to develop low dielectric materials for use in the production of enhanced insulating films.
For example, U.S. Pat. Nos. 3,615,272; 4,399,266; 4,756,977; and 4,999,397 disclose insulating films produced by spin on deposition (SOD) using polysilsesquioxanes with a dielectric constant of about 2.5-3.1 instead of SiO2 with a dielectric constant of 4.0 and deposited by chemical vapor deposition (CVD). Also, hydrogensilsesquioxanes as well as methods for their preparation are well known in the art. For example, U.S. Pat. No. 3,615,272 discloses a method of preparing a completely condensed, soluble hydrogensilsesquioxane, which comprises the steps of condensing trichloro-, trimethoxy- and triacetoxy-silanes in a sulfuric acid medium and then washing the resulting resin with water or aqueous sulfuric acid. U.S. Pat. No. 5,010,159 also discloses a method of synthesizing a condensed hydrogensilsesquioxane resin, which comprises the steps of hydrolyzing hydrosilanes in an arylsulfuric acid hydrate-containing hydrolysis medium and then contacting the resulting resin with a neutralizing agent. U.S. Pat. No. 6,232,424 describes a highly soluble silicone resin composition very stable in solution, which is prepared by hydrolyzing and polycondensing tetraalkoxysilane, organosilane and organotrialkoxysilane monomers in the presence of water and an appropriate catalyst. U.S. Pat. No. 6,000,339 teaches that a silica-based compound, having improved oxygen plasma-resistance, physical properties and thickness of a coating film, can be obtained from the reaction of a monomer selected from the group consisting of an alkoxysilane, a fluorine-containing alkoxysilane and an alkylalkoxysilane and a titanium- or zirconium-alkoxide compound, in the presence of water and an appropriate catalyst. U.S. Pat. No. 5,853,808 discloses that siloxane- and silsesquioxane-based polymers useful for producing SiO2-rich ceramic coatings can be obtained from the hydrolysis and polycondensation of organosilanes possessing a substituted alkyl group. On the other hand, EP 0 997 497 A1 discloses that the hydrolysis and polycondensation of a certain combination of alkoxysilanes including mono-, di-, tri- and tetra-alkoxysilanes as well as trialkoxysilane dimers can provide useful insulating materials. Meanwhile, U.S. Pat. No. 5,378,790 discloses inorganic/organic hybrid materials with excellent physical properties. U.S. Pat. No. 6,660,822 discloses a siloxane-based resin composition obtained from the hydrolysis and polycondensation of circular siloxane monomers and thin insulating films produced from such a composition.
However, insulating films produced using these prior siloxane-based resins cannot achieve a satisfactory low dielectric constant, or they are deficient in mechanical properties and contain excessive carbon even if they have a low dielectric constant. In particular, polymers prepared from a Si compound of Q structure, such as tetramethoxysilane, have good mechanical properties, but their high dielectric constant, due to their inherent strong hygroscopicity, inhibits their use in the production of insulating films, more particularly in the production of insulating films through the SOD process. Recently, siloxane-based resins are required to possess good compatibility with pore-generating substances, usually used for the purpose of further lowering the insulating coefficient thereof.
Consequently, there is a need for developing novel insulating materials that can be applied to the SOD process to provide insulating films with low insulating coefficients and good mechanical properties but also are compatible with pore-generating substances.